Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$149.46	6.757%	$159.559	$159.56	$159.55	$159.60
Purchase #2	$37.43	10.644%	$41.414	$41.41	$41.40	$41.40
Purchase #3	$127.88	7.758%	$137.8009	$137.80	$137.80	$137.80
Purchase #4	$79.78	11.699%	$89.1135	$89.11	$89.10	$89.10
Purchase #5	$119.80	4.805%	$125.5564	$125.56	$125.55	$125.60
Purchase #6	$247.72	5.233%	$260.6832	$260.68	$260.70	$260.70
Purchase #7	$245.89	6.503%	$261.8802	$261.88	$261.90	$261.90
7 purchase totals =	$1,007.96		$1,076.0072	$1,076.00	$1,076.00	$1,076.10